Video information is distributed over a communications network generally in two conventional ways (wireless (i.e., MMDS) and wireline (CATV)). Either of these services can be analog or digital.
A conventional wireless video signal is transmitted in a predetermined frequency range from a one-way broadcast video transmission site in a first polarization (i.e., either horizontal or vertical). The wireless video signal is then received at a customer site in the same polarization, via a video antenna.
To more particularly describe a conventional MMDS video distribution system, refer now to FIG. 1.
FIG. 1 is a block diagram of a conventional video distribution system 100 which, for example, operates over a range of up to 35 miles. A video signal is transmitted from a broadcast video transmission site 106 by an antenna 102 in a given polarization such as horizontal polarization. In this system, the antenna 102 is designed such that cross-polarization polarization rejection is typically at some minimum value such as 20dB. Accordingly, the effective radiated power of this transmitter may be up to hundreds of Watts. The video signal is then received in the same (horizontal) polarization by a video antenna 108 at a customer site 104.
One conventional frequency range that video signals are transmitted in such a system is between 2150-2162 Mhz and 2500-2686 MHz (i.e., 33 6 MHz channels). This frequency spectrum is referred to as a multichannel multipoint distribution system (MMDS).
Background information regarding local multipoint distribution systems (LMDS) (28 GHz) with details of cellular techniques, polarization diversity, spatial diversity, and frequency reuse can be found in U.S. Pat. No. 4,747,160, issued May 24, 1988 to Bossard. Background information regarding point-to-multipoint radio communication system including a master station and a plurality of remote stations which communicate with the master station using frequency division multiplexing can be found in U.S. Pat. No. 4,528,656, issued Jul. 9, 1985 to Morais. Other patents that discuss polarized modulation or the use of horizontal and vertical polarization in the context of radio transmissions include U.S. Pat. No. 2,992,427, issued Jul. 11, 1961 to Franco; U.S. Pat. No. 3,882,393, issued May 6, 1975 to Epstein; U.S. Pat. No. 4,220,923, issued Sep. 2, 1980 to Pelchat et al.; U.S. Pat. No. 4,321,705, issued Mar. 23, 1982 to Namiki; and U.S. Pat. No. 4,521,878, issued Jun. 4, 1985 to Toyonaga. Finally, U.S. Pat. Nos. 3,864,633, issued Feb. 4, 1975 to Stenglein, and 4,525,861, issued Jun. 25, 1985 to Freeburg may be of general relevance.
In analog MMDS systems, as before mentioned, the response channels from the customer site have been limited (typically by FCC regulation) to a small bandwidth (125 kHz wide) for voice or data transmission. The bandwidth of these response channels severely limits their use to transmit information from the customer site to the transmission site. The use of the frequencies are restricted typically by the communication authorities.
Accordingly, what is needed is a system and method for allowing more information to be distributed over a digital MMDS network. The system and method should be easily implemented, cost effective and easily adaptable to existing communication networks. The present invention addresses such a need.